Application of digital dual-phase LIA in the detection of mineral oil in water

In order to protect the environment and save water resources, the oil content of the reinjected water from the oilfield was tested. This paper is based on the digital dual-phase lock-in amplifier (LIA) technology to realize the detection of the weak fluorescence signal emitted by the mineral oil after being stimulated. When the frequency difference between the detection frequency and the center frequency $\mathrm{f}_{\text{mod}}=125 \text{Hz}$ is 0.5 Hz, the detection data is only 2% of the center frequency at most. A standard solution with a concentration of 0 ∼ 10mg / L has been prepared. The linear goodness of the fitting function between the oil concentration in water and the relative fluorescence intensity is $\mathrm{R}^{2}=99.82\%$, showing a good linear relationship, and the test error is controlled within 5.25%. And the results show that it can provide an effective basis for the quality detection of oilfield reinjection water.